As stated before, a genuinely allergic response -
( IgE mediated response), is a feature of some with Multiple Chemical Sensitivity in regards to allergy or sensitization to one or more SPECIFIC allergens & this would certainly be detected with a relevant challenge test (eg. Skin-prick test).
The widely reported & previously described effects whereby a sensitivity to multiple toxicants or excitants is experienced (spreading) –would almost certainly NOT show a true allergic response to all of these multiple toxicants, but nevertheless, we are led to believe in the veracity of these statements of problems:

because of the obvious sincerity of the very many Multiple Chemical Sensitivity – environmental illness sufferers with whom we have had dealings over the years

because of the common threads that run between them – ie. many sufferers “tell the same stories” albeit in a different way

because of the well-documented phenomenon of “cross-reaction” in true allergy, whereby a person with an allergy to one material can become truly allergic to another material which may or may not be related!
So, for example, those who are allergic to house dust mite may also be allergic to shrimps & prawns, as all three contain the same allergy-inducing protein – tropomyosin.
Those allergic to one kind of fish are often allergic to many types of fish (which may be only distantly related); - those allergic to hen’s eggs are often allergic to ALL bird’s eggs.
But our immune systems can also be fooled; they can make mistakes & react to totally unrelated materials
which may or may not be chemically similar, such as house dust mite : kiwi fruit cross-reaction or
latex : banana cross-reactions. In regard to Multiple Chemical Sensitivity & multiple allergy, this type of cross-reaction or sensitivity to unrelated materials is called “generalization” or “spreading” (see earlier).
Viewed in this light, Multiple Chemical Sensitivity, even from a 'conventional' medical perspective, is not so far-fetched or esoteric.
A large part of the reason for our immune system mistakes is that our antibodies recognize just a part or a feature of the antigen (excitant) molecule and not the whole molecule so that if the excitant contains a feature which matches our antibody’s binding site it will, or can be, recognized & produce an allergic reaction.

Although most tests for Multiple Chemical Sensitivity
are inconclusive, it has been shown that by MRI
(magnetic resonance imaging) that some with
Multiple Chemical sensitivity have brain dysfunction
(Heuser, Wojdani & Heuser 1992), which may be
relevant to their condition.

Further, Multiple Chemical Sensitivity patients are,
by and large, not looking for sympathy, but are trying,
to the best of their ability, to adapt their habits
& lifestyle so as to mitigate or avoid these problems
of multiple chemical sensitivity/multiple allergy.
Many patients who are suffering multiple chemical
sensitivity report that following the onset of their
problems, they became sensitive to “everything
they breathe, eat & touch”, which is often not far
from the truth, ( refer generalization & spreading
earlier). Many conventional practitioners including
GPs seem to
believe that, whilst sincere in their beliefs, that
many Multiple Chemical Sensitivity sufferers are
simply misguided in relation to their ailments; this
is probably because these practitioners may have
had minimal contact with multiple chemical
sensitivity sufferers – as their own such patients
may only number one or two – and so they do not
acquire a deeply convincing experience of
multiple chemical sensitivity/chemical injury
characterisics from a spectrum of sufferers.

Over many years, we have had contact with very many different sufferers of multiple chemical sensitivity, environmental illness & myalgic encephalomyelitis who report many different excitants causing many & varied problems, such as, for example:-

Over many years, we have had contact with very many different sufferers of multiple chemical sensitivity, environmental illness & myalgic encephalomyelitis who report many different excitants causing many & varied problems, such as, for example:-

petrol fumes: dizziness, nausea, headache.

Formaldehyde : stinging eyes & nose, breathlessness.

Paint fumes: headache, flu-like symptoms, nausea.

Tap water: itching skin, eczema, breathlessness.

Magazines: breathlessness, wheezing.

Newspapers: breathlessness, headache.

Sugar: stomach ache, bloatedness, nausea.

Flour improvers: stomach pain, digestive upset.

Aspirin: wheezing, eczema, skin problems.

Tartrazine: wheezing, breathlessness, eczema.

Perfumes: asthma-like problems, skin problems.

Cosmetics: skin problems, breathlessness.

Cleaning products: wheezing, eczema, nausea.

Jewellery: skin irritation, itching.

Cigarette smoke: wheezing, headache, nausea.

Department stores: wheezing, stinging eyes, fatigue.

Electrical appliances: multiple problems.

Isocyanate: asthma-like, headache, nausea, eyes itch.

Furniture treatments: headache, asthma-like symptoms.

Carpet treatments : ditto.

Clothing / fabric treatments: ditto.

This is not an exhaustive list of excitants for multiple chemical sensitivity – multiple allergy sufferers, but a few examples of the types of materials & situations that can cause problems – (see our alphabetical list of triggers / issues).
On exposure to such an excitant, the sufferer who was “well” just prior to exposure will often very quickly suffer

By far the best course of action at this point is avoidance of further exposure & removal of the patient to fresh air or a different environment.

A problem at this stage of multiple chemical sensitivity is that many others around at the same time may well not be able to detect anything -much less be affected by it - & may tend to be of the opinion that the sufferer is “over-reacting” when this is not the case.
To those who would ask “How real is multiple chemical sensitivity?” – we would say very real; it can cause endless suffering, the loss of jobs & income, lead to the end of relationships & marriage & cause actual & attempted suicide.
But to multiple chemical sensitivity sufferers, we would say -
Don’t despair – armed with the right advice, there IS hope, there IS help and there IS light at the end of the tunnel.